Re: [RFC PATCH] powerpc/32: Switch VDSO to C implementation.

[Andy Lutomirski]

On Tue, Oct 22, 2019 at 6:56 AM Christophe Leroy
<christophe.leroy@xxxxxx> wrote:
>
>
> >>> The performance is rather disappoiting. That's most likely all
> >>> calculation in the C implementation are based on 64 bits math and
> >>> converted to 32 bits at the very end. I guess C implementation should
> >>> use 32 bits math like the assembly VDSO does as of today.
> >>
> >>> gettimeofday:    vdso: 750 nsec/call
> >>>
> >>> gettimeofday:    vdso: 1533 nsec/call
> >
> > Small improvement (3%) with the proposed change:
> >
> > gettimeofday:    vdso: 1485 nsec/call
>
> By inlining do_hres() I get the following:
>
> gettimeofday:    vdso: 1072 nsec/call
>

A perf report might be informative.